In concrete wall, mine roof and rock wall support systems (hereinafter collectively referred to as mine roof support systems), it is known to stabilize ground forces by first embedding longitudinally elongated reinforcing tendons in bore or drill holes drilled into the rock complex, and then tightening a nut against the wall or rock face to compress and consolidate rock forces.
To form drill holes, pneumatically operated boring tools, such as a hand-held or ground supported stoper or jackleg is used. The boring tools are provided with a reciprocally movable air-leg, to which is coupled a drill steel or rod. The reciprocal movement of the air-leg is used to drive the drill steel into the rock face to a desired depth preferably selected at between about 6 and 12 feet. Typically, anchor or reinforcing tendons consist of a six or twelve foot long steel rebar, a cone bolt or a cable or strand bolt which is provided with a series of bosses or bulges along its length. To permit the tightening of the nut used to provide rock compression, the outermost end of the tendon which protrudes from the rock face is threaded or otherwise adapted to receive the tensioning nut or other fastener which may be tightened against the rock face. The reinforcing tendons are fixedly retained in the drill hole by either mechanical couplers which are activatable to frictionally engage the sides of the drill hole, or through adhesion by the use of mixed grouts or resins.
Where grout or resins are used to adhere tensioning members in place, typically a number of two-part resin or grout (hereinafter collectively referred to as resin) cartridges are pre-inserted into the bore hole immediately ahead of the reinforcing tendon. The tendon is then inserted into the drill hole with a sufficient force to rupture or pierce the resin cartridges. Once properly seated, the tendon is thereafter spun or rotated about its longitudinal axis to assist in the mixing of the resin to ensure more complete setting.
The applicant has appreciated that the length of conventional reinforcing tendons used in mine roof support systems, and the requirement of seating the tendon into elongate drill holes against the resistive forces of both multiple unruptured resin/grout cartridges, and the viscous forces of the released resin, makes the manual insertion of the tendon in the bore hole both difficult and time consuming. Furthermore, if the tendon is not fully seated in the bore hole and spun before the anchoring resin sets, the tendon may not be positioned at a sufficient depth in the rock complex to provide reliable consolidating forces. This in turn may result in either the failure of the anchor tendon, or in a worst case scenario rock wall failure.
In an effort to overcome the difficulties associated with manual positioning of reinforcing tendons, mechanical devices have been proposed for pushing reinforcing tendons into drill holes formed in rock complexes. Conventional tendon pushing apparatus typically include a pair of power driven counter rotating drive wheels. The drive wheels are positioned a distance apart so as to frictionally engage opposing sides of a tendon moved therebetween. In this manner, the rotation of the wheels drives the tendon in forward movement into the drill hole. The requirement of providing a separate apparatus, however, to position reinforcing tendons has not achieved widespread acceptance in the mining industry, as a result of the increased costs and inconvenience associated with providing and transporting separate drilling and positioning tools to a mine work site.
In addition, in underground mining operations dust, dirt and mining debris frequently results in the jamming of the drive wheels often binding the reinforcing tendon therein, and necessitating frequent repair and/or replacement.